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Forest expansion in Scotland and its potential effects on black grouse Tetrao tetrix conservation
Forest Ecology and Management 308 (2013) 145–152
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Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco
Forest expansion in Scotland and its potential effects on black grouse Tetrao tetrix conservation Patrick J.C. White a,⇑, Philip Warren b, David Baines b a b
Game & Wildlife Conservation Trust, Upland Research Group, Drumochter Lodge, Dalwhinnie, Inverness-shire PH19 1AF, UK Game & Wildlife Conservation Trust, Upland Research Group, The Coach House, Eggleston Hall, Barnard Castle, County Durham DL12 0AG, UK
a r t i c l e
i n f o
Article history: Received 16 May 2013 Received in revised form 17 July 2013 Accepted 20 July 2013 Available online 26 August 2013 Keywords: Afforestation Black grouse Conservation Moorland Wildlife habitat Wildlife management
a b s t r a c t Increasing forest cover has been the policy of various countries in recent decades. The Scottish government aims to increase national forest cover from 18% to 25% by 2050. Mid-altitude upland areas above farmland and below the natural tree line will be targeted for planting, which could impact black grouse Tetrao tetrix, a species of conservation concern which is most abundant in this zone. We used lek counts, counts of black grouse shot on sporting estates and habitat data in the Tay region to investigate distributions of black grouse in relation to forest and non-forest habitat composition. Moorland was generally selected relative to forest habitats. Planting of new forests was linked to establishment of leks and maturing of forests was linked to lek extinctions. Between 1945 and 2010, including a previous period of incentivised forest expansion, shooting densities (birds shot per km2) were significantly correlated with the area of pre-thicket (<14 years) forestry in the Tay study area, increasing as it was planted but decreasing as it matured to a closed-canopy structure. Across three Scottish regions (Argyll, Inverness and Galloway) habitat composition within 1 km of leks was similar at 45–60% moorland and 10–15% young forest suggesting this habitat composition may provide a template for designing mosaics that can sustain viable populations in the face of forest expansion. Protection of moorland patches and provision of young forest over a smaller but more consistent area may benefit the species’ conservation. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Landscape changes are driven via many social, economic and cultural factors (Nelson et al., 2006). Specific government policies can impact landscapes which in turn can influence populations of individual species. For example, the European Union’s Common Agricultural Policy increased agricultural production, and indicators such as national cereal yield were strong negative correlates of farmland bird populations (Donald et al., 2001). In recent decades various governments have created national afforestation strategies including Thailand (Food and Agriculture Organization of the United Nations, 2009), India (Kishwan et al., 2007), Ethiopia (Bane et al., 2008) and Ireland (Department of Agriculture, Food and Forestry, 1996). In the UK, government policy in the 20th century included tax relief for commercial forestry that led to a major period of commercial afforestation between the 1950s and the 1980s which lead to a doubling of Britain’s forest cover (Mason, 2007). This had effects on Scotland’s landscape and biodiversity. In north-west Scotland commercial afforestation led to the displacement of breeding dunlin Caladris alpina (Lavers and Haines-Young, 1997), while some species are considered to have ⇑ Corresponding author. Tel.: +44 (0) 1528 522300. E-mail address: [email protected] (P.J.C. White). 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.07.038
benefitted from this change, such as siskins Carduelis spinus and lesser redpolls Carduelis cabaret (Avery and Leslie, 1990). For reasons including carbon sequestration and timber supply security, Scottish Government policy aims to increase forest cover again in Scotland, from 18% to 25% by 2050, split 3:2 as ‘productive’ forest and ‘non-productive’ forest (Forestry Commission Scotland, 2006). The first phase proposes 1000 km2 of new forest (1.3% of the land area) by 2022 (Woodland Expansion Advisory Group, 2012). Black grouse were once widespread in the British Isles, but have declined in both numbers and range over the past century (Hancock et al., 1999; Sharrock, 1976). In the early 1990s an estimated 25,000 males remained (Baines and Hudson, 1995) but by 2005 the number of males had declined to 5100, of which two thirds were found in Scotland (Sim et al., 2008). Between 1996 and 2005, numbers in Scotland declined by 29%, with 49% and 69% declines in southern Scotland whilst in northern areas numbers remained stable (Sim et al., 2008). Black grouse are now recognised as a ‘Priority Species’ of the UK Biodiversity Action Plan’ (Anonymous, 1995) with its own Species Action Plan to restore both numbers and range. They are associated with mosaics of moorland, coniferous plantations, rough grazing fields and meadows (Baines, 1990). In Scotland between the 1950s and 1980s almost all planting occurred on heather moorland, rough grassland and blanket mire (Mackey et al., 1998; Mather and Murray,
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1987). Black grouse initially responded favourably to the establishment of commercial conifer plantations on heather moorland, but resultant canopy closure and the shading out of favoured ground vegetation, has led to subsequent declines (Cayford, 1993; Pearce-Higgins et al., 2007). More emphasis is now placed on biodiversity considerations in the management and placement of new forests (Scottish Government, 2009) compared to afforestation during the late 20th century (e.g. Moss et al., 1979). In this study we investigated how forest and non-forest habitat in the landscape influenced the species’ distribution and abundance through evaluating changes in numbers of black grouse in the Tay region of Scotland between 1992 and 2010 in relation to habitat composition change. To examine if the Tay region was representative of other Scottish populations and to put our findings in a national context we examined variation in habitat cover type composition around leks in three other widespread Scottish regions (Argyll, Galloway and Inverness) in 2007. To assess long term effects of afforestation we compared changes in forest cover and structure in the Tay region in relation to black grouse shooting data (counts of the number of birds shot for sport) between 1945 and 2010. We discuss the extent to which forest expansion policy may influence black grouse populations across Scotland and draw inference as to how placement and timing of afforestation could be managed to achieve the dual aims of afforestation and black grouse conservation in Scotland.
2. Materials and methods Black grouse lek data were assessed from four regions of Scotland, Tay, Argyll, Galloway and Inverness (Fig. 1). The Tay region was subject to an intensive area-based survey over 530 km2 and so we assumed that all leks in the area had been located. For the other regions, however, counts were targeted to within approximately 1 km of the National Forest Estate (Scotland’s state-owned forests) which is made up of irregular areas, so we could not define a landscape area in which presence and absence of leks had been fully established. Forests in these areas were dominated by commercial coniferous forests principally made up of Sitka spruce Picea sitchensis and lodgepole pine Pinus contorta. Also present were semi-natural broadleaf woodlands, principally of birch Betula spp. and ‘‘new native pinewoods’’ composed primarily of Scots pine Pinus sylvestris. The latter are non-commercially afforested areas aimed at restoring Scotland’s native woodland, funded via government grants. Non-forest habitats were dominated by heather Calluna vulgaris moorland and farmland. Black grouse males attending leks within the Tay region were first subject to a full survey in 1992 by staff of the Game & Wildlife Conservation Trust staff and by the Perthshire Black Grouse Study Group. In 2010 the same full area was re-surveyed by these same organisations. Separately, Black grouse were fully surveyed on the National Forest Estate by Forest Enterprise Scotland staff in
Fig. 1. Locations and regional designations (see legend) of leks in Scotland for which data were used in this study. Grey shaded areas represent the National Forests Estate (Scotland’s state-owned forests). The cross-hatched area represents the approximate Tay region study area, representing a minimum convex polygon around all lek locations and their 1 km radii, extended outwards by 3 km for visibility.
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2007, locating 19 leks in the Argyll region, 26 in the Galloway region and 51 in the Inverness region. Data were not available for these regions for 1992 or 2010, so years of surveying differed between Tay and the other regions. Like a previous study of lek and habitat associations, we excluded single displaying males from analyses (Hjeljord and Fry, 1995). They made up 2.8% of males in Tay in 1992 and 1.6% in 2010, 9% of males in Argyll, 14% in Galloway and 4% in Inverness. Overall, 5% of males recorded were displaying as singles. After exclusion of single males, a total of 45 leks were recorded in the Tay region 1992 and 30 in 2010. Count methodology consisted of two site visits during the peak lekking period (Baines, 1996) one during the second half of April and one during the first half of May. Observers searched for displaying males according to a now national-standard protocol (Sim et al., 2008). Visits were made within the first two hours after dawn, avoiding extremely wet or windy weather conditions. The count for a lek was recorded as the maximum number of males observed over both visits. We categorised the study areas into three non-forest and six forest habitat cover types (Table 1). These cover types were defined principally in terms of homogeneous land-use but there were clear vegetation structure and composition differences between them. Commercial forestry stands were split into pre-thicket and closed-canopy based on previous black grouse studies which have shown that numbers increase in pre-thicket stands but decline rapidly at canopy-closure, when preferred ground vegetation declines (Cayford, 1993). It was necessary to define canopy closure by plantation age rather than direct tree metrics since data were not available for the latter over such a wide area. However, data show that cover of ground-layer vascular plants decline sharply after 10–14 years in Sitka spruce plantations (the majority of plantations in our study areas), and 10–19 years in pine plantations (Hill, 1979). Additionally, within even-aged commercial plantations in Tay, a study found that densities of males and females in August peaked at between 4 and 8 years after planting but had fallen to zero at approximately 14 years (Baines et al., 2000). Therefore we defined closed-canopy compartments as aged 14 years or more since planting, acknowledging that there may be some variability between and within stands. We delineated homogeneous habitat
147
patches via a combination of drawing polygons from satellite images and forestry stock-maps, which consist of information about the species and planting year of stands. We digitised them using MapInfo GIS software (MapInfo Corporation, 2011) and checked the data via field-visits. We also used forestry stock maps to examine how areas of pre-thicket and closed-canopy commercial forest in the Tay region varied between 1945 and 2010. This includes the previous period of incentivised afforestation that was encouraged under tax relief for commercial plantings when planting accelerated following the Second World War and ceased in 1988. The composition of cover types was measured within a 1 km radius (3.14 km2) of leks. This radius was selected because in the Tay region the mean distance between adjacent leks was 1.7 km (±0.1 se) in 1992 and 2.1 km (±0.2 se) in 2010, so the majority of cover within in a given radius would be closest to the lek at its centre. It is also assumed to contain the majority of black grouse breeding habitat. For example, in a northern England population 72% (n = 151) of nests were within 1 km of a lek (Warren et al., 2011). We equally split any areas of overlapping radii, separately for 1992 and 2010 in the Tay region. Mean overlap was 5.3%, so areas measured around leks were only reduced by a mean of 2.7%. In the Tay region we defined three sub-groups of lek sites: those present in 1992 that had become extinct in 2010, those that were maintained between 1992 and 2010 and those that were not present in 1992 but had established by 2010. Lek sites are typically traditional as younger males tend to occupy vacant on-lek territories (Havan Wiley, 1974). While their precise location may drift locally over time we considered that leks that were 1 km apart or more between 1992 and 2010 could be considered different lek sites. We calculated change of each habitat within a 1 km radius of a site between 2010 and 1992. We defined the Tay study area as a minimum convex polygon containing all Tay leks and their 1 km radii and extracted overall composition of cover for the area for 1992 and 2010. Compositional analysis within R 2.11.0 (R Core Development Team, 2010) was used to investigate lek-cover associations. This allowed the proportions of cover types within a lek radius to be rendered linearly independent of each other and for multivariate
Table 1 Descriptions of cover types defined in the study and their dominant tree-layer and field layer components. Cover type Non-forest Moorland
Farmland Other
Description Open land previously/currently managed for red grouse shooting and/or red deer Cervus elaphus stalking; some extensive sheep Ovies aries or cattle Bos primigenius grazing; little deer exclusion. Rarely few scattered trees/scrub with field dominated by heather, purple moor-grass Molinia caerulea or peat moss Sphagnum spp More intensively grazed pasture typically at lower altitudes; generally improved; some cereal fields. Occasional tree line along boundary and grass (Poaceae) dominated field layer Areas unsuitable for black grouse, e.g. buildings, roads and water bodies
Non-commercial forest Broadleaf Typically along riparian zones or moorland margins. Birch dominant tree layer with some rowan Sorbus aucuparia, aspen, Populus tremula and woodland willows Salix spp., and grass dominated field layer New native On previous moorland, 14 years old or less; sparsely planted Scots pine trees in clumps with approximately 20% open ground in between with pinewood some birch, rowan and oak Quercus spp. Fenced against red-deer and sheep intrusion; planted under government subsidy. Field layer similar to moorland Commercial forest Unplanted forestry Clearfell forestry Closed-canopy forestry Pre-thicket forestry
Areas enclosed within commercial forestry not planted, including tracks/rides; also areas where severe crop failure has left open areas. Deer generally excluded or lethally controlled. Field layer generally similar to moorland Commercial forestry stands that have been harvested but not restocked. Field layer dominated by brash layer with ericaceous shrubs or grass regenerating between Densely planted commercial forestry stands of primarily Sitka spruce and lodgepole pine where crop canopy has closed over (14 years or older). Generally little field layer Densely planted commercial forestry stands of primarily Sitka spruce and lodgepole pine where crop canopy has yet to close over (under 14 years old). Generally ericaceous shrubs or grass dominating between trees. In 1992, predominantly 1st generation stands, and in 2010 primarily 2nd generation stands.
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analyses to be carried out to investigate the effects of factorial and/or continuous covariates (Aebischer et al., 1993a, 1993b). We excluded the ‘other’ cover type (see Table 1) from compositional analyses as no birds in a separate telemetry study of black grouse in the Tay region were recorded within it (unpubl. data). We examined (a) whether there was apparent selection for cover types within 1 km of lek sites when compared to cover across the Tay study area; (b) whether certain cover types in the Tay region were more associated with leks that went extinct between 1992 and 2010 or had become established between 1992 and 2010; and (c) whether certain cover types were associated with a smaller or larger lek size in the four regions in the years leks were monitored (Tay in 1992 and 2010, all other regions in 2007). For analyses (a) and (c) we carried out analyses for each year separately, because the cover types available or within lek radii differed between years. Our independent variables for compositional analyses were (a) a binary variable ‘area considered’ (study site or 1 km radius around lek; their comparison constitutes analysis of selection), (b) a binary variable ‘lek fate’ between 1992 and 2010 (extinct or established), and (c) a continuous variable ‘lek size’ which was square-root transformed so that it did not significantly differ from normality. Our dependent variables for (a) and (c) were natural log-ratios of all but one cover types over the remaining cover type (farmland was selected arbitrarily as the denominator cover type, but the choice of denominator will not influence the compositional analysis results, see Aebischer et al., 1993a). For (b) our dependent variables were the natural log-ratios of change in all-but-one cover types over the remaining cover type (clearfell forestry was used as the denominator). In the initial multivariate analysis-of-variance (MANOVA) stage of compositional analysis we used non-parametric MANOVA because we could not assume multivariate normality (Aebischer et al., 1993a). Our MANOVA test statistic was Wilk’s K (Aebischer et al., 1993a) where comparing paired availability and use (selection analyses) or Anderson’s (2001) F for lek fate and lek size analyses. Where MANOVA showed a significant effect a ranking matrix (Aebischer et al., 1993b) was constructed for that variable, that indicated which of each pair of cover types was more associated with either (a) lek areas versus the study site, (b) extinct versus established lek sites, or (c) a higher or lower value of lek size. Cover types were excluded from any analyses if (a) they were not available in that year or not present around at least two leks, (b) they did not change in cover between 1992 and 2010 or (c) if they were not present around at least half of leks. Exclusion of such cover types should have minimal effect on interpretation, since excluded habitats made up a small proportion of cover. For cover types excluded in (a) new native pinewood made up 0% of habitat in 1992 and clearfell forestry and pre-thicket forestry made up 1.1% of habitat each in 2010, while in (c) clearfell forestry and pre-thicket forestry made up only 0.1% and 3.6% of habitat in 2010. Cover types were ranked by the number of other cover types they exceeded. Randomisation tests (Kabacoff, 2011) were used to carry out pairwise tests between cover types at P = 0.05. Multiple pairwise tests are standard within compositional analyses (Aebischer et al., 1993b) and we did not adjust our a-level for multiple tests (Gotelli and Ellison, 2004). To examine which cover types were most consistently present around leks we compared between regions the mean composition of each cover type within 1 km of leks and the proportion of leks containing each cover type within 1 km. To assess relative variation in cover types between regions we calculated the between-region coefficient of variation (CV) of each cover type for each measure using the equation CV = r/l, where r represents the between regions standard deviation and l represents the between regions mean. We also calculated the between region CV for
pre-thicket forestry combined with new native pinewood as ‘young forest’. In some regions young forest consisted of almost entirely one or the other, while in terms of black grouse these are potentially functionally equivalent in providing breeding and foraging cover containing young trees that are likely to be used as cover from predators for nests and chicks (Signorell et al., 2010). CVs were calculated across only Argyll, Galloway and Inverness as these data were for the same year (2007), whilst Tay region data were for 1992 and 2010 so were not directly comparable. For 1946–2010 inclusive we obtained annual counts of black grouse shot on 20–26 estates in the county of Perthshire from the National Gamebag Census (Aebischer and Baines, 2008) as an index of relative abundance over this period for an area that included the Tay region study area. Counts of black grouse shot were reported from 97% of estate-years. These were converted to annual shooting densities by dividing the number of birds shot on each estate in each year by the size of that estate (birds shot per km2) and then taking a mean across all estates for each year. Such shooting data have been shown to be reliable indicators of abundance, as measured by counts of live birds for the red grouse Lagopus lagopus scotica (Cattadori et al., 2003). To examine the relationship between the cover of pre-thicket forest and relative black grouse abundance between 1946 and 2010 we carried out a Pearson’s correlation between the availability of pre-thicket forest in our Tay study area and the annual shooting density across the estates. We assumed that forestry change in the Tay study area would be broadly representative of that across Perthshire in which it was fully contained. 3. Results 3.1. Cover change and lek distributions in the Tay region Habitats within the Tay region changed between 1992 and 2010 (Table 2). There were four types of habitat patch change. Moorland was converted to new native pinewood in 4.6% of the area, but leaving 54.0% moorland cover. An equal area of closed-canopy forestry in 1992 had become either clearfell or pre-thicket forestry by 2010 (both 1.1% of study area, but as 6.5% of the study area had matured from pre-thicket to closed-canopy forestry, the total cover of closed-canopy forestry increased from 16.3% to 20.6%. The number of lekking males in the Tay region fell by 14% between 1992 and 2010 (354–306) (Table 2). Males in 2010 occupied 33% fewer lek sites, with the mean lek size 29% larger. Underlying this change in numbers of leks was an extinction of 30 out of 45 of the leks, but an establishment of 15 new leks representing a distributional shift of leks within the region, i.e. 67% of lek sites occupied in 1992 were no longer occupied in 2010 and 50% of lek sites occupied in 2010 had not been established in 1992. Moorland was the most abundant cover type within 1 km of leks in both years and increased between 1992 and 2010 with means of 56% and 67% (Table 2). The largest changes in cover type composition occurred with pre-thicket forestry which fell from 15% within 1 km of leks to 0%. However, new native pinewood, a structurally similar cover type, increased from 0% to 11%. Extinct lek sites had, on average, 5% of their area planted as new native pinewood, while established and maintained lek sites had 11% and 13% (Table 3). Additionally, extinct lek sites had, on average, 20% of their area mature from pre-thicket to closed-canopy forestry, while for established and maintained lek sites this was 3% and 5%. Extinct lek sites also had less adjacent moorland than those that became established or maintained (40% compared to 65% and 66%). We found significant selection at the scale of the lekking group in 1992 (K = 0.59, P = 0.002) and in 2010 (K = 0.15, P = 0.002) with ranking matrices in Table 4. In 1992 Moorland was significantly
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Table 2 Summary of lek data within the study, with mean composition of cover types within 1 km of leks and percentage of leks with the cover type present within 1 km, by year and region. Tay region data were collected by the Perthshire Black Grouse Study Group (PBGSG) and Game & Wildlife Conservation Trust (GWCT) staff in 1992 and 2010. National Forest Estate data were collected by Forest Enterprise Scotland (FES) staff in 2007 only. Cover types represent the percentage present in each given area (±SE). ‘CV’ is the coefficient of variation across three regions for which data were available for the same year (Argyll, Galloway and Inverness in 2007) and cover types have been ranked according to this CV (lowest to highest). ‘Gallow.’ = Galloway, ‘Inver.’ = Inverness. ‘PT + NP’ represents the sum of the new native pinewood and pre-thicket forestry cover types. Data
Tay region data (GWCT & PBGSG)
National Forest Estate data (FES) for 2007
1992
2010
Argyll
Gallow.
Invern.
CV
No. of leks No. of males
45 354
30 306
19 95
26 135
51 438
– –
Composition around leks Moorland Closed-canopy forestry Unplanted forestry Clearfell forestry Pre-thicket forestry (PT) Broadleaf woodland Farmland New native pinewood (NP) PT + NP
56 ± 4 8±2 5±1 0 15 ± 3 7±1 9±2 0 15 ± 3
67 ± 4 6±2 1±0 0 0 5±1 9±2 11 ± 4 11 ± 4
43 ± 8 17 ± 5 16 ± 4 3±1 10 ± 3 6±2 2±2 3±1 13 ± 3
50 ± 7 25 ± 4 12 ± 3 3±1 9±2 1±0 0 0 9±2
58 ± 4 14 ± 2 6±1 1±0 2±1 5±1 2±1 12 ± 3 15 ± 3
0.15 0.30 0.44 0.49 0.62 0.66 0.87 1.25 0.25
Percentage of leks Moorland Broadleaf woodland Closed-canopy forestry Clearfell forestry Unplanted forestry Farmland Pre-thicket forestry (PT) New native pinewood (NP) PT + NP
96 80 71 0 80 64 51 0 51
100 50 64 21 46 32 27 46 64
89 73 92 42 88 12 77 0 73
81 73 92 42 88 12 77 0 77
94 61 71 31 61 22 33 41 71
0.07 0.10 0.14 0.17 0.20 0.38 0.41 1.73 0.04
Table 3 Table for cover types in the Tay region study area, within 1 km of leks that became extinct and within 1 km of leks that became established in 1992 and 2010. For clarity zeroes have been replaced by ‘–’. Study area
Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
Lek became extinct
Lek maintained
1992
2010
1992
2010
1992
2010
1992
2010
58.6 7.1 6.6 – 5.1 16.3 – 6.5
54.0 7.1 6.6 4.6 5.1 20.6 1.1 1.1
45.1 10.2 7.5 – 6.2 10.9 – 20.0
39.9 10.2 7.5 5.2 6.2 29.4 0.6 0.9
78.7 6.9 5.5 – 1.4 3.0 – 4.5
65.6 6.9 5.5 13.1 1.4 7.1 0.3 0.1
75.5 12.0 4.3 – 1.2 4.2 – 2.8
65.0 12.0 4.3 10.5 1.2 6.8 0.1 0.1
selected relative to farmland, pre-thicket forestry and closed-canopy forestry, while unplanted forestry was selected relative to pre-thicket and closed-canopy forestry. In 2010, moorland was selected relative to all other habitats. Extinct and established leks showed significantly different habitat change between 1992 and 2010 (F1.44 = 3.23, P = 0.023) with change in new native pinewood relative to clearfell and closed-canopy forestry being associated positively with leks that became established, or negatively with leks that became extinct. Lek size was related to habitat composition in 2010 F1,28 = 3.51, P = 0.023), but not in 1992 (F1,43 = 0.44, P = 0.699). In 2010 the cover of farmland relative to moorland, unplanted forestry and closed-canopy forestry was negatively related to lek size.
Lek became established
abundant cover type around leks (43–48%) and present around the most number of leks (89–94%), having the lowest between region CV. CVs varied substantially between cover types for both composition and presence around leks and in both cases closedcanopy forestry also had a relatively low CV (0.30 and 0.14) and were present in a relatively high proportion of lek radii (71–92%). Young forest components, new native pine forest and pre-thicket forestry combined were present in relatively similar proportions across regions (9–15%), being present around 71–73% of leks and had relatively low CVs for composition around leks (0.25) and percentage of leks present around (0.04).
3.3. Changes in forest cover in relation to black grouse shooting bags 3.2. Between-region variation There was no significant relationship between lek size and cover type composition in 2007 for Inverness (F1,49 = 0.30, P = 0.884), Argyll (F1,17 = 1.05, P = 0.347) or Galloway (F1,24 = 1.50, P = 0.182). Cover type compositions within 1 km of leks contrasted among the three regions (Table 3). Moorland was consistently the most
The cover of commercial forest stands in the Tay region increased relatively steadily between 1945 and 1988 but then levelled off (Fig. 2). However, while the area of closed-canopy forestry generally increased over time, that of pre-thicket forestry reached a peak in 1971, and a smaller peak in 1990, before reducing substantially to a low level in the 2000s. Between 1945 and 2010 black grouse shooting density fluctuated (Fig. 2) but was significantly
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Table 4 Ranking matrices for the Tay region data for: (a) cover type selection within 1 km of leks relative to the study site in 1992 and 2010; (b) lek fate, comparing cover type change between established and extinct leks, between 1992 and 2010 and (c) relationship between cover type composition and square root of lek size in 1992 and 2010. The +/- sign shows that the numerator cover type was higher/lower ranked with respect to the appropriate analysis and is tripled (+++/—) where the pairwise difference was significant. Numerator cover types are ranked according to the number of higher rank (+ or +++) positions, with the highest number indicating the highest degree of selection. Cover types not ranked were excluded due to lack of availability, change between 1992 and 2010 or presence within 1 km of leks. Analysis
Numerator cover type
Denominator cover type
Rank
Unplanted ClosedMoorland Farmland Broadleaf New forestry canopy woodland native forestry pinewood Selection 1992 (ranked most to least) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry Selection 2010 (ranked most to least) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry Lek fate 1992–2010 (ranked established to extinct)
+++
+ -
— -
+
-
+ -
+ -
—
-
-
+++
+++ +
— — — — —
-
+ -
Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
Lek size (ranked largest to smallest) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
+ -
+++ + -
— + +
positively correlated with the area of pre-thicket in the Tay study area (r = 0.64, t40 = 6.64, P < 0.001).
4. Discussion 4.1. Black grouse lek distributions and cover type composition Moorland remained the most common and consistent cover type around leks across regions and across time in the Tay region. Leks that went extinct had lower adjacent moorland components than leks that became established. We could not compare to availability in the other regions, but in Tay moorland was selected relative to other cover types in both 1992 and 2010. Moorland is a key cover type for breeding and lekking (Baines, 1990; Parr and Watson, 1988) which is maintained in the long term by grazing, browsing and burning unlike the transitional nature of young forests. Moorland and young forest proximity could complement each other in terms of providing breeding cover type for a lekking group by providing a more diverse array of vegetation structures. Substantial forest cover changes occurred in the Tay study area between 1992 and 2010. The observed distributional shift of leks in the region was related to the extinction of leks where pre-thicket forestry matured (which is consistent with previous studies: Baines et al., 2000; Pearce-Higgins et al., 2007) and the establishment of leks near to new native pinewoods, revealing the impor-
+ + +++ +++
+ + +
5 2 3
+++
+++ -
4 0
-
+
1
+++ + + +
+++ + + + -
5 4 2 3 0 1
+
— — + -
+++ + +
—
+
+++
+++ + +
—
-
+
Clearfell Preforestry thicket forestry
+ + +
+
+
-
2
+++
+++
+
4
-
-
0 1 3
+ + — +
— -
+
3 0 1 2 4 5
tance of young forest in driving change in lek distributions. Shooting data also indicated a relationship between abundance of young forest and abundance of black grouse in the Tay region which, although correlative, matches patterns seen in previous studies (Pearce-Higgins et al., 2007). This is likely to be attributable to their importance as good breeding habitat (Baines et al., 2000), including their provision of better cover for chicks from aerial predators (Signorell et al., 2010). The presence of young forest around lek sites was relatively consistent across regions, although its nature varied across regions, from almost entirely pre-thicket forestry in Galloway, to almost entirely new native pine forest in Tay. The maturation of forests is linked to reductions in breeding females and lekking males and productivity is the key demographic factor determining black grouse populations (Baines, 1991; Baines et al., 2007).
4.2. Management considerations Favourable habitat needs to be provided at the lek scale, but also connected at the landscape scale to facilitate connectivity between lekking groups to allow dispersal between populations (Caizergues and Ellison, 2002) and to facilitate genetic exchange (Höglund et al., 2011). New planting schemes should not only consider implications for existing leks but also on connectivity between populations. Given that across regions and over time leks
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Fig. 2. Areas of pre-thicket and closed-canopy forestry (stacked) in the Tay study area since 1945 and mean number of birds shot per km2 on 27 estates in Perthshire, the county containing the Tay study area, between 1948 and 1989.
were situated with approximately 50–70% moorland within 1 km (approximately 150–200 ha), an important management consideration is how to maintain sufficiently large and well-connected areas of moorland as a consistent long-term breeding habitat. This creates a potential conflict with afforestation where space is limited. Further investigation of the patch size, quality and connectivity or moorland required by black grouse is required. Remaining moorland areas may require better grazing management to provide higher quality habitats to mitigate future effects of maturation in surrounding forests. For example, grazing pressure can influence the availability of key shrub species that provide high invertebrate biomass and nest sites, while under-grazing can potentially lead to rank vegetation that restricts chick movement (Calladine et al., 2002). Lek data suggest an average of 10–15% young forest is typical within 1 km of lek sites (approximately 30–50 ha). Given that black grouse shift distributions in response to young forest availability, this may give an indication of the area most beneficial to lekking groups. Proximity to moorland is likely to be important in avoiding local population crashes by allowing breeding females associated with a lek to use moorland to breed when the forest matures. The logistics of providing young forest over the long term, however, are complicated given the length of forest cycles. Our historical forest stock map data for the previous period of incentivised afforestation show that where planting is relatively consistent over time, the area of young forest can decrease rapidly and be relatively scarce in a region after cessation of planting. This issue is compounded by the fact that non-productive forest areas, which are intended to comprise 40% of the target are not designed for felling and re-stocking, so may effectively ‘remove’ moorland and young forest components from the spatiotemporal cover mosaic over a long-term. It may be important that areas planted are on moorland that is considered of lower quality for black grouse. Ideally, a period of afforestation in an area should be longer than the length of a typical forest cycle (40–60 years), so that the felling and re-stocking of early plantings overlaps with late plantings. Mature forest components such as closed-canopy forestry and broadleaved woodland were present near the majority of leks. These may be important in providing alternative food sources in winter during periods of snow lie (Warren et al., 2013). Similarly, in spring, larch Larix spp. buds are known to provide a protein resource for black grouse for breeding (Baines, 1990). Given the component of forest already present in the landscape and the likely long-term increase in this resource, it seems unlikely that these components will be a limiting factor in the future. However, providing some forest components to sparsely forested areas could potentially benefit local populations in severe winters.
4.3. Conclusions Black grouse conservation must be balanced against timber and other ecosystem service requirements when planning national forest expansion in Scotland. Our results suggest that the protection of moorland and managing forest cycles to provide a smaller but more consistent young forest component over time could reduce potential negative impacts on black grouse. Forest expansion will inevitably cause local shifts in the distribution of black grouse populations and afforestation should be managed locally such that these shifts do not fragment remaining populations and exclude black grouse from significant areas of their current range. Acknowledgments This work was funded by Scottish Natural Heritage, Cairngorms National Park Authority, Forest Enterprise Scotland (FES) and members of the Game and Wildlife Conservation Trust. Thanks to the Perthshire Black Grouse Study Group and FES for providing lek data and numerous keepers, landowners and farmers for allowing access for lek counts and contributing shooting data. Nicholas Aebischer provided statistical advice and Julie Ewald GIS advice. Phoebe Morton, Holly Stevens, Gemma Jenkins and Merlin Becker assisted with habitat mapping. References Aebischer, N.J., Baines, D., 2008. Monitoring gamebird abundance and productivity in the UK: the GWCT long-term datasets. Revista Catalana d’Ornitologia 24, 30– 43. Aebischer, N.J., Marcstrom, V., Kenward, R.E., Karlbom, M., 1993a. Survival and habitat utilisation: a case for compositional analysis. In: Marked Individuals in the Study of Bird Population. Birkhauser Verlag, Basel. Aebischer, N.J., Robertson, P.A., Kenward, R.E., 1993b. Compositional analysis of habitat use from animal radio-tracking data. Ecology 74, 1313–1325. Anonymous, 1995. Biodiveristy: The UK Sterring Group Report – Volume 2 Action Plans. Her Majesty’s Stationary Office, London. Avery, M., Leslie, R., 1990. Birds and Forestry. T & AD Poyser, London. Baines, D., 1990. The ecology and conservation of black grouse in Scotland and northern England. In: Lumeij, I.T., Hoogeveen, Y.R. (Eds.), The Future of Wild Galliformes in the Netherlands. Gegevens Koninklijke Bibliotheek, The Hague, pp. 106–118. Baines, D., 1991. Factors contributing to local and regional variation in black grouse breeding success in Northern Britain. Ornis Scandinavica 22, 264. Baines, D., 1996. Seasonal variation in lek attendance and lekking behaviour by male Black Grouse Tetrao tetrix. Ibis 138, 177–180. Baines, D., Hudson, P.J., 1995. The decline of black grouse in Scotland and northern England. Bird Study 42, 122–131. Baines, D., Blake, K., Calladine, J., 2000. Reversing the decline: a review of some black grouse conservation projects in the United Kingdom. Cahiers d’Ethologie 20, 217–234. Baines, D., Warren, P., Richardson, M., 2007. Variations in the vital rates of black grouse Tetrao tetrix in the United Kingdom. Wild. Biol. 13 (Suppl. 1), 109–116.
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Bane, J., Nune, S., Mekonnen, A., Bluffstone, R., 2008. Policies to Increase Forest Cover in Ethiopia‘. Environmental Economics Policy Forum for Ethiopia, Addis Ababa. Caizergues, A., Ellison, L.N., 2002. Natal dispersal and its consequences in Black Grouse Tetrao tetrix. Ibis 144, 478–487. Calladine, J., Baines, D., Warren, P., 2002. Effects of reduced grazing on population density and breeding success of black grouse in northern England. J. Appl. Ecol. 39, 772–780. Cattadori, I.M., Haydon, D.T., Thirgood, S.J., Hudson, P.J., 2003. Are indirect measures of abundance a useful index of population density? The case of red grouse harvesting. Oikos 100, 439–446. Cayford, J.T., 1993. Black Grouse and Forestry: Habitat requirements and management. Forestry Commission Technical Paper 1. Forestry Commission, Edinburgh. Department of Agriculture, Food and Forestry, 1996. Growing for the Future: a Strategic Plan for the Development of the Forestry Sector in Ireland. The Stationary Office, Dublin. Donald, P.F., Green, R.E., Heath, M.F., 2001. Agricultural intensification and the collapse of Europe’s farmland bird populations. Proc. R. Soc. B: Biol. Sci. 268, 25– 29. Food and Agriculture Organization of the United Nations, 2009. Asia-Pacific Forestry Sector Outlook Study II: Thailand Forestry Outlook Study. Food and Agriculture Organization of the United Nations, New York. Forestry Commission Scotland, 2006. The Scottish Forestry Strategy. Forestry Commission Scotland, Edinburgh. Gotelli, N.J., Ellison, A.M., 2004. A Primer of Ecological Statistics. Sinauer Associates Inc., Sunderland. Hancock, M., Baines, D., Gibbons, D., Etheridge, B., Shepherd, M., 1999. Status of male Black Grouse Tetrao tetrix in Britain in 1995–96. Bird Study 46, 1–15. Havan Wiley, R., 1974. Evolution of social organization and life-history patterns among grouse. Quart. Rev. Biol. 49, 201–227. Hill, M.O., 1979. The development of a flora in even-aged plantations. In: Ford, E.D., Malcom, D.C., Atterson, J. (Eds.), The Ecology of Even-aged Forest Plantations. Institute of Terrestrial Ecology, Cambridge, pp. 175–192. Hjeljord, O., Fry, G., 1995. The size of black grouse lek populations in relation to habitat characteristics in Southern Norway. In: Proceedings of the 6th International Grouse Symposium. Instituto Nazionale per la Fauna Selvatica, Udine, Italy, pp. 67–70. Höglund, J., Larsson, J.K., Corrales, C., Santafé, G., Baines, D., Segelbacher, G., 2011. Genetic structure among black grouse in Britain: implications for designing conservation units. Anim. Conserv. 14, 1–9. Kabacoff, R.I., 2011. R in Action: Data Analysis and Graphics with R. Manning Publications Co., Shelter Island. Kishwan, J., Pandey, D., Goyal, A.K., Gupta, A.K., 2007. India’s Forests. Ministry of Environment and Forests, New Delhi.
Lavers, C.P., Haines-Young, R.H., 1997. Displacement of dunlin Calidris alpina schinzii by forestry in the Flow Country and an estimate of the value of moorland adjacent to plantations. Biol. Conserv. 79, 87–90. Mackey, E.C., Shewry, M.C., Tudor, G.J., 1998. Land Cover Change: Scotland from the 1940s to the 1980s. Scottish Natural Heritage, Edinburgh. MapInfo Corporation, 2011. MapInfo Professional Version 11.0. Pitney Bowes MapInfo, Troy. Mason, W.L., 2007. Changes in the management of British forests between 1945 and 2000 and possible future trends. Ibis 149 (Suppl. 2), 41–52. Mather, A.S., Murray, N.C., 1987. Employment and private-sector afforestation in Scotland. J. Rural Stud. 3, 207–218. Moss, D., Taylor, P.N., Easterbee, N., 1979. The effects on song-bird populations of upland afforestation with spruce. Forestry 52, 129–150. Nelson, G., Bennett, E., Berhe, A., Cassman, K., DeFries, R., Dietz, T., Dobermann, A., Dobson, A., Janetos, A., Levy, M., Marco, D., Nakicenovic, N., O’Neill, B., Norgaard, R., Petschel-Held, G., Ojima, D., Pingali, P., Watson, R., Zurek, M., 2006. Anthropogenic drivers of ecosystem change: an overview. Papers in Natural Resources. Parr, R., Watson, A., 1988. Habitat preferences of black grouse on moorlanddominated ground in north-east Scotland. Ardea 76, 175–180. Pearce-Higgins, J.W., Grant, M.C., Robinson, M.C., Haysom, S.L., 2007. The role of forest maturation in causing the decline of Black Grouse Tetrao tetrix. Ibis 149, 143–155. R Core Development Team, 2010. R Version 2.11.0. R Foundation for Statistical Computing, Vienna. Scottish Government, 2009. The Scottish Government’s Rationale for Woodland Expansion. The Scottish Government, Edinburgh. Sharrock, J.T.R., 1976. The Atlas of Breeding Birds in Britain and Ireland. T & AD Poyser, Calton. Signorell, N., Wirthner, S., Patthey, P., Schranz, R., Rotelli, L., Arlettaz, R., 2010. Concealment from predators drives foraging habitat selection in brood-rearing Alpine black grouse Tetrao tetrix hens: habitat management implications. Wild. Biol. 16, 249–257. Sim, I.M.W., Eaton, M.A., Setchfield, R.P., Warren, P., Lindley, P., 2008. Abundance of male Black Grouse Tetrao tetrix in Britain in 2005, and change since 1995–96. Bird Study 55, 303–315. Warren, P., Baines, D., Richardson, M., 2011. Black grouse Tetrao tetrix nest-site habitats and fidelity to breeding areas in northern England. Bird Study 59, 139– 143. Warren, P., White, P.J.C., Baines, D., Atterton, F., Brown, M.B., 2013. Variations in Black Grouse Tetrao tetrix winter survival in a year with prolonged snow cover. Bird Study 60, 257–263. Woodland Expansion Advisory Group, 2012. Report of the Woodland Expansion Advisory Group to the Cabinet Secretary for Rural Affairs and Environment Richard Lochhead, MSP. Woodland Expansion Advisory Group, Edinburgh.
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Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco
Forest expansion in Scotland and its potential effects on black grouse Tetrao tetrix conservation Patrick J.C. White a,⇑, Philip Warren b, David Baines b a b
Game & Wildlife Conservation Trust, Upland Research Group, Drumochter Lodge, Dalwhinnie, Inverness-shire PH19 1AF, UK Game & Wildlife Conservation Trust, Upland Research Group, The Coach House, Eggleston Hall, Barnard Castle, County Durham DL12 0AG, UK
a r t i c l e
i n f o
Article history: Received 16 May 2013 Received in revised form 17 July 2013 Accepted 20 July 2013 Available online 26 August 2013 Keywords: Afforestation Black grouse Conservation Moorland Wildlife habitat Wildlife management
a b s t r a c t Increasing forest cover has been the policy of various countries in recent decades. The Scottish government aims to increase national forest cover from 18% to 25% by 2050. Mid-altitude upland areas above farmland and below the natural tree line will be targeted for planting, which could impact black grouse Tetrao tetrix, a species of conservation concern which is most abundant in this zone. We used lek counts, counts of black grouse shot on sporting estates and habitat data in the Tay region to investigate distributions of black grouse in relation to forest and non-forest habitat composition. Moorland was generally selected relative to forest habitats. Planting of new forests was linked to establishment of leks and maturing of forests was linked to lek extinctions. Between 1945 and 2010, including a previous period of incentivised forest expansion, shooting densities (birds shot per km2) were significantly correlated with the area of pre-thicket (<14 years) forestry in the Tay study area, increasing as it was planted but decreasing as it matured to a closed-canopy structure. Across three Scottish regions (Argyll, Inverness and Galloway) habitat composition within 1 km of leks was similar at 45–60% moorland and 10–15% young forest suggesting this habitat composition may provide a template for designing mosaics that can sustain viable populations in the face of forest expansion. Protection of moorland patches and provision of young forest over a smaller but more consistent area may benefit the species’ conservation. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction Landscape changes are driven via many social, economic and cultural factors (Nelson et al., 2006). Specific government policies can impact landscapes which in turn can influence populations of individual species. For example, the European Union’s Common Agricultural Policy increased agricultural production, and indicators such as national cereal yield were strong negative correlates of farmland bird populations (Donald et al., 2001). In recent decades various governments have created national afforestation strategies including Thailand (Food and Agriculture Organization of the United Nations, 2009), India (Kishwan et al., 2007), Ethiopia (Bane et al., 2008) and Ireland (Department of Agriculture, Food and Forestry, 1996). In the UK, government policy in the 20th century included tax relief for commercial forestry that led to a major period of commercial afforestation between the 1950s and the 1980s which lead to a doubling of Britain’s forest cover (Mason, 2007). This had effects on Scotland’s landscape and biodiversity. In north-west Scotland commercial afforestation led to the displacement of breeding dunlin Caladris alpina (Lavers and Haines-Young, 1997), while some species are considered to have ⇑ Corresponding author. Tel.: +44 (0) 1528 522300. E-mail address: [email protected] (P.J.C. White). 0378-1127/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2013.07.038
benefitted from this change, such as siskins Carduelis spinus and lesser redpolls Carduelis cabaret (Avery and Leslie, 1990). For reasons including carbon sequestration and timber supply security, Scottish Government policy aims to increase forest cover again in Scotland, from 18% to 25% by 2050, split 3:2 as ‘productive’ forest and ‘non-productive’ forest (Forestry Commission Scotland, 2006). The first phase proposes 1000 km2 of new forest (1.3% of the land area) by 2022 (Woodland Expansion Advisory Group, 2012). Black grouse were once widespread in the British Isles, but have declined in both numbers and range over the past century (Hancock et al., 1999; Sharrock, 1976). In the early 1990s an estimated 25,000 males remained (Baines and Hudson, 1995) but by 2005 the number of males had declined to 5100, of which two thirds were found in Scotland (Sim et al., 2008). Between 1996 and 2005, numbers in Scotland declined by 29%, with 49% and 69% declines in southern Scotland whilst in northern areas numbers remained stable (Sim et al., 2008). Black grouse are now recognised as a ‘Priority Species’ of the UK Biodiversity Action Plan’ (Anonymous, 1995) with its own Species Action Plan to restore both numbers and range. They are associated with mosaics of moorland, coniferous plantations, rough grazing fields and meadows (Baines, 1990). In Scotland between the 1950s and 1980s almost all planting occurred on heather moorland, rough grassland and blanket mire (Mackey et al., 1998; Mather and Murray,
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1987). Black grouse initially responded favourably to the establishment of commercial conifer plantations on heather moorland, but resultant canopy closure and the shading out of favoured ground vegetation, has led to subsequent declines (Cayford, 1993; Pearce-Higgins et al., 2007). More emphasis is now placed on biodiversity considerations in the management and placement of new forests (Scottish Government, 2009) compared to afforestation during the late 20th century (e.g. Moss et al., 1979). In this study we investigated how forest and non-forest habitat in the landscape influenced the species’ distribution and abundance through evaluating changes in numbers of black grouse in the Tay region of Scotland between 1992 and 2010 in relation to habitat composition change. To examine if the Tay region was representative of other Scottish populations and to put our findings in a national context we examined variation in habitat cover type composition around leks in three other widespread Scottish regions (Argyll, Galloway and Inverness) in 2007. To assess long term effects of afforestation we compared changes in forest cover and structure in the Tay region in relation to black grouse shooting data (counts of the number of birds shot for sport) between 1945 and 2010. We discuss the extent to which forest expansion policy may influence black grouse populations across Scotland and draw inference as to how placement and timing of afforestation could be managed to achieve the dual aims of afforestation and black grouse conservation in Scotland.
2. Materials and methods Black grouse lek data were assessed from four regions of Scotland, Tay, Argyll, Galloway and Inverness (Fig. 1). The Tay region was subject to an intensive area-based survey over 530 km2 and so we assumed that all leks in the area had been located. For the other regions, however, counts were targeted to within approximately 1 km of the National Forest Estate (Scotland’s state-owned forests) which is made up of irregular areas, so we could not define a landscape area in which presence and absence of leks had been fully established. Forests in these areas were dominated by commercial coniferous forests principally made up of Sitka spruce Picea sitchensis and lodgepole pine Pinus contorta. Also present were semi-natural broadleaf woodlands, principally of birch Betula spp. and ‘‘new native pinewoods’’ composed primarily of Scots pine Pinus sylvestris. The latter are non-commercially afforested areas aimed at restoring Scotland’s native woodland, funded via government grants. Non-forest habitats were dominated by heather Calluna vulgaris moorland and farmland. Black grouse males attending leks within the Tay region were first subject to a full survey in 1992 by staff of the Game & Wildlife Conservation Trust staff and by the Perthshire Black Grouse Study Group. In 2010 the same full area was re-surveyed by these same organisations. Separately, Black grouse were fully surveyed on the National Forest Estate by Forest Enterprise Scotland staff in
Fig. 1. Locations and regional designations (see legend) of leks in Scotland for which data were used in this study. Grey shaded areas represent the National Forests Estate (Scotland’s state-owned forests). The cross-hatched area represents the approximate Tay region study area, representing a minimum convex polygon around all lek locations and their 1 km radii, extended outwards by 3 km for visibility.
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2007, locating 19 leks in the Argyll region, 26 in the Galloway region and 51 in the Inverness region. Data were not available for these regions for 1992 or 2010, so years of surveying differed between Tay and the other regions. Like a previous study of lek and habitat associations, we excluded single displaying males from analyses (Hjeljord and Fry, 1995). They made up 2.8% of males in Tay in 1992 and 1.6% in 2010, 9% of males in Argyll, 14% in Galloway and 4% in Inverness. Overall, 5% of males recorded were displaying as singles. After exclusion of single males, a total of 45 leks were recorded in the Tay region 1992 and 30 in 2010. Count methodology consisted of two site visits during the peak lekking period (Baines, 1996) one during the second half of April and one during the first half of May. Observers searched for displaying males according to a now national-standard protocol (Sim et al., 2008). Visits were made within the first two hours after dawn, avoiding extremely wet or windy weather conditions. The count for a lek was recorded as the maximum number of males observed over both visits. We categorised the study areas into three non-forest and six forest habitat cover types (Table 1). These cover types were defined principally in terms of homogeneous land-use but there were clear vegetation structure and composition differences between them. Commercial forestry stands were split into pre-thicket and closed-canopy based on previous black grouse studies which have shown that numbers increase in pre-thicket stands but decline rapidly at canopy-closure, when preferred ground vegetation declines (Cayford, 1993). It was necessary to define canopy closure by plantation age rather than direct tree metrics since data were not available for the latter over such a wide area. However, data show that cover of ground-layer vascular plants decline sharply after 10–14 years in Sitka spruce plantations (the majority of plantations in our study areas), and 10–19 years in pine plantations (Hill, 1979). Additionally, within even-aged commercial plantations in Tay, a study found that densities of males and females in August peaked at between 4 and 8 years after planting but had fallen to zero at approximately 14 years (Baines et al., 2000). Therefore we defined closed-canopy compartments as aged 14 years or more since planting, acknowledging that there may be some variability between and within stands. We delineated homogeneous habitat
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patches via a combination of drawing polygons from satellite images and forestry stock-maps, which consist of information about the species and planting year of stands. We digitised them using MapInfo GIS software (MapInfo Corporation, 2011) and checked the data via field-visits. We also used forestry stock maps to examine how areas of pre-thicket and closed-canopy commercial forest in the Tay region varied between 1945 and 2010. This includes the previous period of incentivised afforestation that was encouraged under tax relief for commercial plantings when planting accelerated following the Second World War and ceased in 1988. The composition of cover types was measured within a 1 km radius (3.14 km2) of leks. This radius was selected because in the Tay region the mean distance between adjacent leks was 1.7 km (±0.1 se) in 1992 and 2.1 km (±0.2 se) in 2010, so the majority of cover within in a given radius would be closest to the lek at its centre. It is also assumed to contain the majority of black grouse breeding habitat. For example, in a northern England population 72% (n = 151) of nests were within 1 km of a lek (Warren et al., 2011). We equally split any areas of overlapping radii, separately for 1992 and 2010 in the Tay region. Mean overlap was 5.3%, so areas measured around leks were only reduced by a mean of 2.7%. In the Tay region we defined three sub-groups of lek sites: those present in 1992 that had become extinct in 2010, those that were maintained between 1992 and 2010 and those that were not present in 1992 but had established by 2010. Lek sites are typically traditional as younger males tend to occupy vacant on-lek territories (Havan Wiley, 1974). While their precise location may drift locally over time we considered that leks that were 1 km apart or more between 1992 and 2010 could be considered different lek sites. We calculated change of each habitat within a 1 km radius of a site between 2010 and 1992. We defined the Tay study area as a minimum convex polygon containing all Tay leks and their 1 km radii and extracted overall composition of cover for the area for 1992 and 2010. Compositional analysis within R 2.11.0 (R Core Development Team, 2010) was used to investigate lek-cover associations. This allowed the proportions of cover types within a lek radius to be rendered linearly independent of each other and for multivariate
Table 1 Descriptions of cover types defined in the study and their dominant tree-layer and field layer components. Cover type Non-forest Moorland
Farmland Other
Description Open land previously/currently managed for red grouse shooting and/or red deer Cervus elaphus stalking; some extensive sheep Ovies aries or cattle Bos primigenius grazing; little deer exclusion. Rarely few scattered trees/scrub with field dominated by heather, purple moor-grass Molinia caerulea or peat moss Sphagnum spp More intensively grazed pasture typically at lower altitudes; generally improved; some cereal fields. Occasional tree line along boundary and grass (Poaceae) dominated field layer Areas unsuitable for black grouse, e.g. buildings, roads and water bodies
Non-commercial forest Broadleaf Typically along riparian zones or moorland margins. Birch dominant tree layer with some rowan Sorbus aucuparia, aspen, Populus tremula and woodland willows Salix spp., and grass dominated field layer New native On previous moorland, 14 years old or less; sparsely planted Scots pine trees in clumps with approximately 20% open ground in between with pinewood some birch, rowan and oak Quercus spp. Fenced against red-deer and sheep intrusion; planted under government subsidy. Field layer similar to moorland Commercial forest Unplanted forestry Clearfell forestry Closed-canopy forestry Pre-thicket forestry
Areas enclosed within commercial forestry not planted, including tracks/rides; also areas where severe crop failure has left open areas. Deer generally excluded or lethally controlled. Field layer generally similar to moorland Commercial forestry stands that have been harvested but not restocked. Field layer dominated by brash layer with ericaceous shrubs or grass regenerating between Densely planted commercial forestry stands of primarily Sitka spruce and lodgepole pine where crop canopy has closed over (14 years or older). Generally little field layer Densely planted commercial forestry stands of primarily Sitka spruce and lodgepole pine where crop canopy has yet to close over (under 14 years old). Generally ericaceous shrubs or grass dominating between trees. In 1992, predominantly 1st generation stands, and in 2010 primarily 2nd generation stands.
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analyses to be carried out to investigate the effects of factorial and/or continuous covariates (Aebischer et al., 1993a, 1993b). We excluded the ‘other’ cover type (see Table 1) from compositional analyses as no birds in a separate telemetry study of black grouse in the Tay region were recorded within it (unpubl. data). We examined (a) whether there was apparent selection for cover types within 1 km of lek sites when compared to cover across the Tay study area; (b) whether certain cover types in the Tay region were more associated with leks that went extinct between 1992 and 2010 or had become established between 1992 and 2010; and (c) whether certain cover types were associated with a smaller or larger lek size in the four regions in the years leks were monitored (Tay in 1992 and 2010, all other regions in 2007). For analyses (a) and (c) we carried out analyses for each year separately, because the cover types available or within lek radii differed between years. Our independent variables for compositional analyses were (a) a binary variable ‘area considered’ (study site or 1 km radius around lek; their comparison constitutes analysis of selection), (b) a binary variable ‘lek fate’ between 1992 and 2010 (extinct or established), and (c) a continuous variable ‘lek size’ which was square-root transformed so that it did not significantly differ from normality. Our dependent variables for (a) and (c) were natural log-ratios of all but one cover types over the remaining cover type (farmland was selected arbitrarily as the denominator cover type, but the choice of denominator will not influence the compositional analysis results, see Aebischer et al., 1993a). For (b) our dependent variables were the natural log-ratios of change in all-but-one cover types over the remaining cover type (clearfell forestry was used as the denominator). In the initial multivariate analysis-of-variance (MANOVA) stage of compositional analysis we used non-parametric MANOVA because we could not assume multivariate normality (Aebischer et al., 1993a). Our MANOVA test statistic was Wilk’s K (Aebischer et al., 1993a) where comparing paired availability and use (selection analyses) or Anderson’s (2001) F for lek fate and lek size analyses. Where MANOVA showed a significant effect a ranking matrix (Aebischer et al., 1993b) was constructed for that variable, that indicated which of each pair of cover types was more associated with either (a) lek areas versus the study site, (b) extinct versus established lek sites, or (c) a higher or lower value of lek size. Cover types were excluded from any analyses if (a) they were not available in that year or not present around at least two leks, (b) they did not change in cover between 1992 and 2010 or (c) if they were not present around at least half of leks. Exclusion of such cover types should have minimal effect on interpretation, since excluded habitats made up a small proportion of cover. For cover types excluded in (a) new native pinewood made up 0% of habitat in 1992 and clearfell forestry and pre-thicket forestry made up 1.1% of habitat each in 2010, while in (c) clearfell forestry and pre-thicket forestry made up only 0.1% and 3.6% of habitat in 2010. Cover types were ranked by the number of other cover types they exceeded. Randomisation tests (Kabacoff, 2011) were used to carry out pairwise tests between cover types at P = 0.05. Multiple pairwise tests are standard within compositional analyses (Aebischer et al., 1993b) and we did not adjust our a-level for multiple tests (Gotelli and Ellison, 2004). To examine which cover types were most consistently present around leks we compared between regions the mean composition of each cover type within 1 km of leks and the proportion of leks containing each cover type within 1 km. To assess relative variation in cover types between regions we calculated the between-region coefficient of variation (CV) of each cover type for each measure using the equation CV = r/l, where r represents the between regions standard deviation and l represents the between regions mean. We also calculated the between region CV for
pre-thicket forestry combined with new native pinewood as ‘young forest’. In some regions young forest consisted of almost entirely one or the other, while in terms of black grouse these are potentially functionally equivalent in providing breeding and foraging cover containing young trees that are likely to be used as cover from predators for nests and chicks (Signorell et al., 2010). CVs were calculated across only Argyll, Galloway and Inverness as these data were for the same year (2007), whilst Tay region data were for 1992 and 2010 so were not directly comparable. For 1946–2010 inclusive we obtained annual counts of black grouse shot on 20–26 estates in the county of Perthshire from the National Gamebag Census (Aebischer and Baines, 2008) as an index of relative abundance over this period for an area that included the Tay region study area. Counts of black grouse shot were reported from 97% of estate-years. These were converted to annual shooting densities by dividing the number of birds shot on each estate in each year by the size of that estate (birds shot per km2) and then taking a mean across all estates for each year. Such shooting data have been shown to be reliable indicators of abundance, as measured by counts of live birds for the red grouse Lagopus lagopus scotica (Cattadori et al., 2003). To examine the relationship between the cover of pre-thicket forest and relative black grouse abundance between 1946 and 2010 we carried out a Pearson’s correlation between the availability of pre-thicket forest in our Tay study area and the annual shooting density across the estates. We assumed that forestry change in the Tay study area would be broadly representative of that across Perthshire in which it was fully contained. 3. Results 3.1. Cover change and lek distributions in the Tay region Habitats within the Tay region changed between 1992 and 2010 (Table 2). There were four types of habitat patch change. Moorland was converted to new native pinewood in 4.6% of the area, but leaving 54.0% moorland cover. An equal area of closed-canopy forestry in 1992 had become either clearfell or pre-thicket forestry by 2010 (both 1.1% of study area, but as 6.5% of the study area had matured from pre-thicket to closed-canopy forestry, the total cover of closed-canopy forestry increased from 16.3% to 20.6%. The number of lekking males in the Tay region fell by 14% between 1992 and 2010 (354–306) (Table 2). Males in 2010 occupied 33% fewer lek sites, with the mean lek size 29% larger. Underlying this change in numbers of leks was an extinction of 30 out of 45 of the leks, but an establishment of 15 new leks representing a distributional shift of leks within the region, i.e. 67% of lek sites occupied in 1992 were no longer occupied in 2010 and 50% of lek sites occupied in 2010 had not been established in 1992. Moorland was the most abundant cover type within 1 km of leks in both years and increased between 1992 and 2010 with means of 56% and 67% (Table 2). The largest changes in cover type composition occurred with pre-thicket forestry which fell from 15% within 1 km of leks to 0%. However, new native pinewood, a structurally similar cover type, increased from 0% to 11%. Extinct lek sites had, on average, 5% of their area planted as new native pinewood, while established and maintained lek sites had 11% and 13% (Table 3). Additionally, extinct lek sites had, on average, 20% of their area mature from pre-thicket to closed-canopy forestry, while for established and maintained lek sites this was 3% and 5%. Extinct lek sites also had less adjacent moorland than those that became established or maintained (40% compared to 65% and 66%). We found significant selection at the scale of the lekking group in 1992 (K = 0.59, P = 0.002) and in 2010 (K = 0.15, P = 0.002) with ranking matrices in Table 4. In 1992 Moorland was significantly
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Table 2 Summary of lek data within the study, with mean composition of cover types within 1 km of leks and percentage of leks with the cover type present within 1 km, by year and region. Tay region data were collected by the Perthshire Black Grouse Study Group (PBGSG) and Game & Wildlife Conservation Trust (GWCT) staff in 1992 and 2010. National Forest Estate data were collected by Forest Enterprise Scotland (FES) staff in 2007 only. Cover types represent the percentage present in each given area (±SE). ‘CV’ is the coefficient of variation across three regions for which data were available for the same year (Argyll, Galloway and Inverness in 2007) and cover types have been ranked according to this CV (lowest to highest). ‘Gallow.’ = Galloway, ‘Inver.’ = Inverness. ‘PT + NP’ represents the sum of the new native pinewood and pre-thicket forestry cover types. Data
Tay region data (GWCT & PBGSG)
National Forest Estate data (FES) for 2007
1992
2010
Argyll
Gallow.
Invern.
CV
No. of leks No. of males
45 354
30 306
19 95
26 135
51 438
– –
Composition around leks Moorland Closed-canopy forestry Unplanted forestry Clearfell forestry Pre-thicket forestry (PT) Broadleaf woodland Farmland New native pinewood (NP) PT + NP
56 ± 4 8±2 5±1 0 15 ± 3 7±1 9±2 0 15 ± 3
67 ± 4 6±2 1±0 0 0 5±1 9±2 11 ± 4 11 ± 4
43 ± 8 17 ± 5 16 ± 4 3±1 10 ± 3 6±2 2±2 3±1 13 ± 3
50 ± 7 25 ± 4 12 ± 3 3±1 9±2 1±0 0 0 9±2
58 ± 4 14 ± 2 6±1 1±0 2±1 5±1 2±1 12 ± 3 15 ± 3
0.15 0.30 0.44 0.49 0.62 0.66 0.87 1.25 0.25
Percentage of leks Moorland Broadleaf woodland Closed-canopy forestry Clearfell forestry Unplanted forestry Farmland Pre-thicket forestry (PT) New native pinewood (NP) PT + NP
96 80 71 0 80 64 51 0 51
100 50 64 21 46 32 27 46 64
89 73 92 42 88 12 77 0 73
81 73 92 42 88 12 77 0 77
94 61 71 31 61 22 33 41 71
0.07 0.10 0.14 0.17 0.20 0.38 0.41 1.73 0.04
Table 3 Table for cover types in the Tay region study area, within 1 km of leks that became extinct and within 1 km of leks that became established in 1992 and 2010. For clarity zeroes have been replaced by ‘–’. Study area
Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
Lek became extinct
Lek maintained
1992
2010
1992
2010
1992
2010
1992
2010
58.6 7.1 6.6 – 5.1 16.3 – 6.5
54.0 7.1 6.6 4.6 5.1 20.6 1.1 1.1
45.1 10.2 7.5 – 6.2 10.9 – 20.0
39.9 10.2 7.5 5.2 6.2 29.4 0.6 0.9
78.7 6.9 5.5 – 1.4 3.0 – 4.5
65.6 6.9 5.5 13.1 1.4 7.1 0.3 0.1
75.5 12.0 4.3 – 1.2 4.2 – 2.8
65.0 12.0 4.3 10.5 1.2 6.8 0.1 0.1
selected relative to farmland, pre-thicket forestry and closed-canopy forestry, while unplanted forestry was selected relative to pre-thicket and closed-canopy forestry. In 2010, moorland was selected relative to all other habitats. Extinct and established leks showed significantly different habitat change between 1992 and 2010 (F1.44 = 3.23, P = 0.023) with change in new native pinewood relative to clearfell and closed-canopy forestry being associated positively with leks that became established, or negatively with leks that became extinct. Lek size was related to habitat composition in 2010 F1,28 = 3.51, P = 0.023), but not in 1992 (F1,43 = 0.44, P = 0.699). In 2010 the cover of farmland relative to moorland, unplanted forestry and closed-canopy forestry was negatively related to lek size.
Lek became established
abundant cover type around leks (43–48%) and present around the most number of leks (89–94%), having the lowest between region CV. CVs varied substantially between cover types for both composition and presence around leks and in both cases closedcanopy forestry also had a relatively low CV (0.30 and 0.14) and were present in a relatively high proportion of lek radii (71–92%). Young forest components, new native pine forest and pre-thicket forestry combined were present in relatively similar proportions across regions (9–15%), being present around 71–73% of leks and had relatively low CVs for composition around leks (0.25) and percentage of leks present around (0.04).
3.3. Changes in forest cover in relation to black grouse shooting bags 3.2. Between-region variation There was no significant relationship between lek size and cover type composition in 2007 for Inverness (F1,49 = 0.30, P = 0.884), Argyll (F1,17 = 1.05, P = 0.347) or Galloway (F1,24 = 1.50, P = 0.182). Cover type compositions within 1 km of leks contrasted among the three regions (Table 3). Moorland was consistently the most
The cover of commercial forest stands in the Tay region increased relatively steadily between 1945 and 1988 but then levelled off (Fig. 2). However, while the area of closed-canopy forestry generally increased over time, that of pre-thicket forestry reached a peak in 1971, and a smaller peak in 1990, before reducing substantially to a low level in the 2000s. Between 1945 and 2010 black grouse shooting density fluctuated (Fig. 2) but was significantly
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Table 4 Ranking matrices for the Tay region data for: (a) cover type selection within 1 km of leks relative to the study site in 1992 and 2010; (b) lek fate, comparing cover type change between established and extinct leks, between 1992 and 2010 and (c) relationship between cover type composition and square root of lek size in 1992 and 2010. The +/- sign shows that the numerator cover type was higher/lower ranked with respect to the appropriate analysis and is tripled (+++/—) where the pairwise difference was significant. Numerator cover types are ranked according to the number of higher rank (+ or +++) positions, with the highest number indicating the highest degree of selection. Cover types not ranked were excluded due to lack of availability, change between 1992 and 2010 or presence within 1 km of leks. Analysis
Numerator cover type
Denominator cover type
Rank
Unplanted ClosedMoorland Farmland Broadleaf New forestry canopy woodland native forestry pinewood Selection 1992 (ranked most to least) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry Selection 2010 (ranked most to least) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry Lek fate 1992–2010 (ranked established to extinct)
+++
+ -
— -
+
-
+ -
+ -
—
-
-
+++
+++ +
— — — — —
-
+ -
Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
Lek size (ranked largest to smallest) Moorland Farmland Broadleaf woodland New native pinewood Unplanted forestry Closed-canopy forestry Clearfell forestry Pre-thicket forestry
+ -
+++ + -
— + +
positively correlated with the area of pre-thicket in the Tay study area (r = 0.64, t40 = 6.64, P < 0.001).
4. Discussion 4.1. Black grouse lek distributions and cover type composition Moorland remained the most common and consistent cover type around leks across regions and across time in the Tay region. Leks that went extinct had lower adjacent moorland components than leks that became established. We could not compare to availability in the other regions, but in Tay moorland was selected relative to other cover types in both 1992 and 2010. Moorland is a key cover type for breeding and lekking (Baines, 1990; Parr and Watson, 1988) which is maintained in the long term by grazing, browsing and burning unlike the transitional nature of young forests. Moorland and young forest proximity could complement each other in terms of providing breeding cover type for a lekking group by providing a more diverse array of vegetation structures. Substantial forest cover changes occurred in the Tay study area between 1992 and 2010. The observed distributional shift of leks in the region was related to the extinction of leks where pre-thicket forestry matured (which is consistent with previous studies: Baines et al., 2000; Pearce-Higgins et al., 2007) and the establishment of leks near to new native pinewoods, revealing the impor-
+ + +++ +++
+ + +
5 2 3
+++
+++ -
4 0
-
+
1
+++ + + +
+++ + + + -
5 4 2 3 0 1
+
— — + -
+++ + +
—
+
+++
+++ + +
—
-
+
Clearfell Preforestry thicket forestry
+ + +
+
+
-
2
+++
+++
+
4
-
-
0 1 3
+ + — +
— -
+
3 0 1 2 4 5
tance of young forest in driving change in lek distributions. Shooting data also indicated a relationship between abundance of young forest and abundance of black grouse in the Tay region which, although correlative, matches patterns seen in previous studies (Pearce-Higgins et al., 2007). This is likely to be attributable to their importance as good breeding habitat (Baines et al., 2000), including their provision of better cover for chicks from aerial predators (Signorell et al., 2010). The presence of young forest around lek sites was relatively consistent across regions, although its nature varied across regions, from almost entirely pre-thicket forestry in Galloway, to almost entirely new native pine forest in Tay. The maturation of forests is linked to reductions in breeding females and lekking males and productivity is the key demographic factor determining black grouse populations (Baines, 1991; Baines et al., 2007).
4.2. Management considerations Favourable habitat needs to be provided at the lek scale, but also connected at the landscape scale to facilitate connectivity between lekking groups to allow dispersal between populations (Caizergues and Ellison, 2002) and to facilitate genetic exchange (Höglund et al., 2011). New planting schemes should not only consider implications for existing leks but also on connectivity between populations. Given that across regions and over time leks
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Fig. 2. Areas of pre-thicket and closed-canopy forestry (stacked) in the Tay study area since 1945 and mean number of birds shot per km2 on 27 estates in Perthshire, the county containing the Tay study area, between 1948 and 1989.
were situated with approximately 50–70% moorland within 1 km (approximately 150–200 ha), an important management consideration is how to maintain sufficiently large and well-connected areas of moorland as a consistent long-term breeding habitat. This creates a potential conflict with afforestation where space is limited. Further investigation of the patch size, quality and connectivity or moorland required by black grouse is required. Remaining moorland areas may require better grazing management to provide higher quality habitats to mitigate future effects of maturation in surrounding forests. For example, grazing pressure can influence the availability of key shrub species that provide high invertebrate biomass and nest sites, while under-grazing can potentially lead to rank vegetation that restricts chick movement (Calladine et al., 2002). Lek data suggest an average of 10–15% young forest is typical within 1 km of lek sites (approximately 30–50 ha). Given that black grouse shift distributions in response to young forest availability, this may give an indication of the area most beneficial to lekking groups. Proximity to moorland is likely to be important in avoiding local population crashes by allowing breeding females associated with a lek to use moorland to breed when the forest matures. The logistics of providing young forest over the long term, however, are complicated given the length of forest cycles. Our historical forest stock map data for the previous period of incentivised afforestation show that where planting is relatively consistent over time, the area of young forest can decrease rapidly and be relatively scarce in a region after cessation of planting. This issue is compounded by the fact that non-productive forest areas, which are intended to comprise 40% of the target are not designed for felling and re-stocking, so may effectively ‘remove’ moorland and young forest components from the spatiotemporal cover mosaic over a long-term. It may be important that areas planted are on moorland that is considered of lower quality for black grouse. Ideally, a period of afforestation in an area should be longer than the length of a typical forest cycle (40–60 years), so that the felling and re-stocking of early plantings overlaps with late plantings. Mature forest components such as closed-canopy forestry and broadleaved woodland were present near the majority of leks. These may be important in providing alternative food sources in winter during periods of snow lie (Warren et al., 2013). Similarly, in spring, larch Larix spp. buds are known to provide a protein resource for black grouse for breeding (Baines, 1990). Given the component of forest already present in the landscape and the likely long-term increase in this resource, it seems unlikely that these components will be a limiting factor in the future. However, providing some forest components to sparsely forested areas could potentially benefit local populations in severe winters.
4.3. Conclusions Black grouse conservation must be balanced against timber and other ecosystem service requirements when planning national forest expansion in Scotland. Our results suggest that the protection of moorland and managing forest cycles to provide a smaller but more consistent young forest component over time could reduce potential negative impacts on black grouse. Forest expansion will inevitably cause local shifts in the distribution of black grouse populations and afforestation should be managed locally such that these shifts do not fragment remaining populations and exclude black grouse from significant areas of their current range. Acknowledgments This work was funded by Scottish Natural Heritage, Cairngorms National Park Authority, Forest Enterprise Scotland (FES) and members of the Game and Wildlife Conservation Trust. Thanks to the Perthshire Black Grouse Study Group and FES for providing lek data and numerous keepers, landowners and farmers for allowing access for lek counts and contributing shooting data. Nicholas Aebischer provided statistical advice and Julie Ewald GIS advice. Phoebe Morton, Holly Stevens, Gemma Jenkins and Merlin Becker assisted with habitat mapping. References Aebischer, N.J., Baines, D., 2008. Monitoring gamebird abundance and productivity in the UK: the GWCT long-term datasets. Revista Catalana d’Ornitologia 24, 30– 43. Aebischer, N.J., Marcstrom, V., Kenward, R.E., Karlbom, M., 1993a. Survival and habitat utilisation: a case for compositional analysis. In: Marked Individuals in the Study of Bird Population. Birkhauser Verlag, Basel. Aebischer, N.J., Robertson, P.A., Kenward, R.E., 1993b. Compositional analysis of habitat use from animal radio-tracking data. Ecology 74, 1313–1325. Anonymous, 1995. Biodiveristy: The UK Sterring Group Report – Volume 2 Action Plans. Her Majesty’s Stationary Office, London. Avery, M., Leslie, R., 1990. Birds and Forestry. T & AD Poyser, London. Baines, D., 1990. The ecology and conservation of black grouse in Scotland and northern England. In: Lumeij, I.T., Hoogeveen, Y.R. (Eds.), The Future of Wild Galliformes in the Netherlands. Gegevens Koninklijke Bibliotheek, The Hague, pp. 106–118. Baines, D., 1991. Factors contributing to local and regional variation in black grouse breeding success in Northern Britain. Ornis Scandinavica 22, 264. Baines, D., 1996. Seasonal variation in lek attendance and lekking behaviour by male Black Grouse Tetrao tetrix. Ibis 138, 177–180. Baines, D., Hudson, P.J., 1995. The decline of black grouse in Scotland and northern England. Bird Study 42, 122–131. Baines, D., Blake, K., Calladine, J., 2000. Reversing the decline: a review of some black grouse conservation projects in the United Kingdom. Cahiers d’Ethologie 20, 217–234. Baines, D., Warren, P., Richardson, M., 2007. Variations in the vital rates of black grouse Tetrao tetrix in the United Kingdom. Wild. Biol. 13 (Suppl. 1), 109–116.
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